High-speed downlink packet data services are of importance to the success of third-generation (3G) and beyond, wireless systems. Examples of such systems include CDMA2000 (see, e.g., 3GPP2 C.S0024 Version 4.0, CDMA2000 High Rate Packet Data Air Interface Specification, December 2001); the High Data Rate (HDR) system which is described in an article entitled CDMA/HDR: a bandwidth-efficient high-speed wireless data service for nomadic users, that was authored by P. Bender et al., and appeared in IEEE Communications Magazine, pp. 70-77 in July 2000; High Speed Data Packet Access (HSDPA) as described in the 3GPP Technical Specification 25.308 version 5.2.0, entitled High Speed Downlink Packet Access (HSDPA): Overall Description, published in March 2002. As is generally known, each of the systems employs Time-Division Multiple Access (TDMA) techniques to provide sharing of a downlink data channel among multiple users.
To facilitate the deployment and effectiveness of such systems, supporting technologies, such as transmission techniques and scheduling methods are being explored and characterized. Specifically, at the physical layer, Multiple-Input Multiple-Output (MIMO) antenna techniques are attractive because they can increase the channel capacity between a base station (BS) and an individual user due, in part, to the spatial (antenna) diversity. At the media access control (MAC) layer, a scheduler within the BS selects users for transmission according to their channel-state-information (CSI) feedback and their measured throughput performance, characterizing their multiuser diversity as was described by M. Grossglauser and D. Tse, in an article entitled “Mobility increases the capacity of ad hoc wireless networks”, which appeared in IEEE/ACM Trans. Networking, Vol. 10, No. 4, pp 477-486 in August 2002.
As can be appreciated, both types of diversity identified above play a central role in systems that exhibit high throughput and fair resource allocation among users.
Multiple-Input Multiple Output (MIMO) antenna techniques, (see, e.g., S. M. Alamouti, “A Simple Transmit Diversity Technique for Wireless Communications”, IEEE J. Select. Areas Commun., vol 16, No. 8, pp. 1451-1458, Oct. 1998; G. J. Foschini, “Layered Space-Time Architecture for Wireless Communication In a Fading Environment When Using Multi-Element Antennas”, Bell Labs Technical Journal, vol. 1, No. 2, pp. 41-59, Autumn 1996; and I. E. Telatar, “Capacity Of Multi-Antenna Gaussian Channels”, European Trans. On Telecommun., vol 10, pp. 585-595, November-December 1999). One of these techniques, Orthogonal Space-Time Block Coding (STBC) was recently adopted for implementation as one of the transmission diversity modes in 3G wireless networks (See, for example, V. Tarokh, H. Jafarkhani, and A. R. Calderbank, “Space-Time Block Codes From Orthogonal Designs”, IEEE Trans. Inform. Theory, vol. 45, no 5, pp. 1456-1467, July 1999). The STBC technique advantageously achieves “full transmit diversity” and reliable channel(s), however it does not exhibit particular transmission efficiency.
Another technique, the Vertical Bell Labs Layered Space-Time (V-BLAST) technique, which was described in a paper authored by P. Wolniansky, G. J. Foschini, G. D. Golden, and R. A. Valenzuela entitled “V-BLAST: An Architecture For Realizing Very High Data Rates Over the Rich-Scattering Wireless Channel” which appeared in Proc. Int. Symp. Sig. Sys. Elect. (ISSSE), in Pisa, Italy in September 1998 and another paper authored by G. J. Foschini, G. D. Golden, R. A. Valenzuela and P. W. Wolniasky entitled “Simplified Processing For High Spectral Efficiency Wireless Communication Employing Multi-Element Arrays”, that appeared in IEEE J. Select. Areas. Commun., vol 17, No 11, pp. 1841-1852 and published in November 1999, provides high-rate data transmission but is less reliable during instantaneous deep fades.
Scheduling methods, and in particular scheduling methods for selecting a particular user to whom access to a system should be granted have likewise been the subject of much investigation. More specifically, certain methods grant access to the user that can most efficiently use the system—the one with the best/strongest channel thereby having the highest data rate. In such systems, throughput is maximized at the expense of users using less desirable channels. One such system, was described in U.S. Pat. No. 6,449,491 for Transmitter Directed Code Division Multiple Access System Using Path Diversity To Equitably Maximize Throughput which issued to Chaponniere et al on Sep. 10, 2002, determined an access metric for each user and provided channel access to that user having the greatest access metric.
Alternative scheduling methods have been explored that provide channel access to all users equally—regardless of channel efficiency or throughput. With such systems, the equal access—which may be based on time/duration or volume of transmission—sacrifices overall system efficiency for equality of access.
In addition, methods such as the Maximum Carrier-to-Interference Ratio (max-C/I) scheduling which was described by R. Knopp and P. A. Humbler, in a paper entitled “Information Capacity and Power Control in Single Cell Multiuser Communications”, which appeared Proc. IEEE Int. Conf. Commun. (ICC), at pp. 331-335, in June 1995; the Proportionally Fair (PF) scheduling method as described in a paper entitled “Data Throughput of CDMA-HDR A High Efficiency-High Data Rate Personal Communication Wireless System”, authored by A. Jalali, R. Padovani, and R. Pankaj, that was published in Proc. IEEE Veh. Technol. (VTC), at pages 1854-1858 in May 2000; and a paper by P. Viswanath, D. N. C. Tse and R. Laroia, entitled “Opportunistic Beamforming Using Dumb Antennas” that appeared in IEEE Trans. On Inform. Theory, vol. 48, No. 6, pp. 1277-1294 in June 2002; and the wired, Max-Min Fair scheduling method as described by D. Bertsekas and R. Gallagar in Data Networks, Chapter 6, published by Prentice-Hall of Englewood Cliffs, N.J. in 1992 all offer particular advantages/disadvantages which characterize their method.
More specifically, each of the above methods differs in the performance of aggregate downlink throughput and the fairness as it relates to per-user time/throughput. Each (except Max-Min Fair) however, is channel-dependent in that they all rely on instantaneous CSI feedback as opposed to the simpler, Round-Robin (RR) scheduling where users are selected independently of channel status.
Accordingly, there exists a continuing need for methods that provide fair access to users of shared wireless systems, while maintaining overall system efficiency. Such method(s) is/are the subject of the present invention.